Conventionally, in the fields of printing, electronic industry and the like, light irradiation apparatuses for radiating light of specific wavelengths have been heavily used to perform curing treatment, drying treatment, melting treatment, softening treatment, modification treatment or the like on objects to be treated, such as a protective film, an adhesive, paint, ink, photoresist, a resin and an alignment film.
For example, Patent Literature 1 discloses an inkjet printer that uses an ultraviolet-curable ink. This inkjet printer includes a head unit that ejects the ink, and a light irradiation apparatus that is installed next to this head unit. In such an inkjet printer, the head unit includes a plurality of discharge parts. Then, these discharge parts eject various types of ink (photocurable material) to a recording medium. The light irradiation apparatus then irradiates the ink ejected to the recording medium with light.
However, if the foregoing inkjet printer is used for a long period of time, the amounts of ink ejected from the discharge parts may become unstable. One of the reasons for the occurrence of such a phenomenon is that the discharge parts of the head unit are directly or indirectly irradiated with the light from the light irradiation apparatus disposed next to the head unit, so that the ink cures in the discharge parts and the cured products interfere with the ejection of the ink from the discharge parts.
In particular, optical fabrication apparatuses, typified by a 3D printer, form a three-dimensional structure on a surface to be irradiated. The resulting three-dimensional structure can thus reflect the light from the light irradiation apparatus, and the reflected light is likely to be projected on the discharge parts of the head unit. This results in a problem that the phenomenon is likely to occur in which the amounts of photocurable material ejected from the discharge parts become unstable.
To solve such a problem, Patent Literature 2 discloses an inkjet printer in which a light irradiation apparatus is separated from a head unit by a distance L and the light irradiation apparatus is obliquely disposed, whereby the projection of the light from the light irradiation apparatus upon the discharge parts of the head unit is suppressed.
However, such an inkjet printer has the problem that the entire apparatus becomes large in size since the light irradiation apparatus is separated from the head unit by a considerably large distance and is obliquely disposed.